Casimir IV the Jagiellonian (Polish: Kazimierz Jagiellończyk, Lithuanian Kazimieras Jogailaitis) (1427 - 1492), of the House of Jagiello was grand duke of Lithuania from 1440 and king of Poland from 1447 until his death.
The son of king Wladislaus II Jagiełło and younger brother to Wladislaus III, Casimir succeeded the latter after a three-year interregnum. He married in 1454 Elisabeth, the daughter of Albert II of Habsburg. The marriage strengthened the ties between the houses of Jagiello and Habsburg.
A daughter, Jadwiga, was married to George the Rich Wittelsbach of Bavaria. Delegates had gone to Kraków to negotiate the marriage. Their so-called Landshut Wedding took place in Bavaria with much pomp and celebration in 1475.
His son named Casimir was to have been married to the daughter of emperor Frederick III but he instead chose a religious life, eventually becoming canonized as St. Casimir and his son Hungary and Bohemia.
Casimir belongs to that remarkable group of late medieval sovereigns who may be called the fathers of modern diplomacy, inasmuch as they relegated warfare to its proper place as the instrument of politics, and preferred the councilchamber to the battle-field.
In his youth Casimir was considered frivolous and licentious; while his sudden flight from the field of Plowce, the scene of his fathers great victory over the Teutonic knights, argued but poorly for his personal courage.
Fortunately Casimir was a mini of npnptrstin,i c~eniiis T-Tis fiitlier hsd hp~n ii 1,prn whri trusted entirely to his sword, yet the heroic struggle of a lifetime bad barely sufficed to keep at bay the numerous and potent foes with which Poland was environed.